The present invention relates, in general, to a device for controlling drives in machine tools or production machines.
Nothing in the following discussion of the state of the art is to be construed as an admission of prior art.
In a modern machine tool or production machine, which can include, for example, a motor with a connected gear and load, a controller is typically associated with each drive. One controller can hereby simultaneously control several motors. The efficiency and the quality of almost all drives in machine tools and production machines depend directly on an optimized dynamic characteristic of the drive controller. A suitable test functionality for ensuring the desired control characteristic of the machine is therefore desirable.
A commercially available device for controlling drives in machine tools or production machines and for performing tests includes an internal trace module for recording signals, as well as an internal signal generator. The signal generator is used to add test signals to the control functions of the device as a measure of the excitation. The test signals can be, for example, a step excitation of a controller setpoint. In conventional, commercially available function generators, a user can only select a limited number of curve forms, for example, a step function, digital noise, a sine function and certain parameters (amplitude, offset, period duration, etc.). For performing the test, a trigger signal which can be generated by an external diagnostic/startup device, can trigger the trace module as well as the function generator. The function generator then adds the aforedescribed curve functions with predefined parameters to the control functions of the device, and records after triggering actual process values, which are also predefined through parameters, such as signals from external transducers or other signals within the control functions of the device. The user can then download to, for example, the diagnostic/startup device, the actual process values, that are non-permanently stored in the trace module, and evaluate the actual process values, wherein the signal curves are stored in the form of binary files that do not employ a standardized file format.
Another known test function is the so-called circularity test, which can only be performed in the presence of a supervisory controller. An application program in the supervisory controller generates a circular path in Cartesian coordinates. When the circularity test is selected, the supervisory controller configures, triggers and/or starts the trace module during the execution of the application program. However, the application program and the trace module are not precisely synchronized. Instead, the user has to initially start the application program, which includes following the path of a continuous circle, and subsequently activate the circularity test. The circularity test automatically compares the desired circle and the actual circle and determines the maximum deviations. These deviations are displayed on the user interface of the controller, but cannot be further processed directly by a supervisory automation plane or Internet services.
Because the aforedescribed circularity test is only a special test of a quality check of a machine tool or production machine and cannot be generally applied, it is customary to produce test workpieces in order to verify the accuracy and the dynamics of the machine. Because a test workpiece has typically a limited size, the machine characteristic is only checked in a correspondingly small portion of the machine workspace.
As mentioned above, the actual process values recorded by the trace module are not permanently stored and are also not stored in a standard file format, but have to be first transferred to an external startup/diagnostic device. The user can therefore not evaluate if, for example, the variation in the actual rotation speed during a change of the desired rotation speed stays within an acceptable limit, because for example process reference values recorded during the startup of the machine are no longer available for comparison. Another problem is that for a comprehensive evaluation, a startup/diagnostic device must always be connected to the device that controls the drive(s).
It is therefore desirable to permanently store actual process values that are recorded by a trace functionality, in particular by a trace module, in a standard file format in the device that controls the drives.